Another Breech for a Crosman. Part 2

Right where I left off...

























Picked up the edge of the breech then cranked the table to center.

With a 7/8" ball mill, I cut the radius to fit against the gas tube.

It was a pretty slow cut and produced a lot of chips.

The last pass was done at high speed taking off about a thousandth.  Gave an acceptable finish.

Back to the mill (after some chip clean up) and spotted the hole for the rear breech screw.

Through drilled.

Drilled for the forward breech screw.

0.250" hole for the transfer port.

Set the X-stops.





 













Milled the slot for the hammer cocking pin.

Not shown:  Drilled three #29 holes for barrel set screws.  Went through the small taps and found a #8-32 plug tap.

Tapped.

Flipped the breech--this is the top--and countersunk the rear breech screw hole.

Left turn(side), Clyde.  Set the table stops for the bolt handle slot.  That's a 3/16" end mill.

A few passes later.  Yep, cleaned up the chips before taking the picture.

This contraption is a tilting table.  Allows the work to be angled relative to the spindle.  I set it at about 12 degrees fahrenheit.




 













This is a train wreck.  The breech is in an insert vise that's been bolted and step-clamped to the top of the table.

All for this little cut.

Should let the bolt handle angle downward when locked in the forward position.

Marked out the location for the loading slot.

0.750" end mill looked about right.

Just breaking through the 0.250" through hole for the loading bolt.




 













Luckily (OK, I did actually measure first) I didn't break through at the front into the 0.4375" hole for the barrel.   Would've still worked though.

Lined up on the front breech bolt through hole...

and counterbored for the head of the fastener.



More in a couple days.

Yep, I Need Another Breech for a Crosman. Part 1

There's a pile of projects on my to-do list, but this appealed to me the most.  I'd like to make another breech for a Crosman 22XX-type gun.  Something simple this time.  There's no plan to make it a repeater like the last time around. 















Starting with a piece of 6061 aluminum. 

I finally got around to purchasing a 4-jaw independent chuck for the lathe.

Put off getting a 4-jaw because I couldn't figure out which chuck to order.  (and there wasn't a pressing need)  Eventually, I broke down and just picked out a 6" diameter "plain back" chuck then made an adapter plate-- a "back plate" in machinisty terminology.  The "back plate" adapts the chuck to the spindle of the machine. 





















Scribed a center line on the face of the aluminum and adjusted the chuck until the line centered up with a pointed indicator held in the tail stock.

Notice the offset.






















Spotted the hole and all looks good.  The offset is easier to see here.  this is part of the advantage of a 4-jaw chuck.  Offsetting work as well as the ability to hold work that isn't round, triangular or hex shaped.

This piece of aluminum is 6" long and I'm drilling a 0.250" hole all the way through.  The flutes need constant clearing as well as lubrication with a cutting fluid to prevent the aluminum from welding to the cutting edges.   It's a very laborious process to drill a hole this deep.  And the smaller the diameter of the drill bit, the harder the job becomes as the bit wants to flex and walk the hole out of alignment by the time it breaks through on the far side.  Slow going, can't force the bit. 

Finally through.  There's 6.25" of drill bit through the aluminum here.  If I make another breech, I'll use a 0.375" drill bit for the through-hole.  The bump-up in drill size make for a more rigid set up. 

It gets easier now.  The .250" hole is partially drilled out with a .4375"  bit--the same diameter as a Crosman 22XX barrel.    I drilled this hole for the barrel just shy of 3.175" deep.  The painter's tape on the bit gave me a quick and dirty depth measurement.

Followed with a 0.4375" reamer.  A spot of dykem on the shank and a scribed line made it easy to hit the exact depth.

As I'm not a fan of the way the "soda straw" Crosman barrel looks, I'm going to add a barrel shroud to bring the barrel up in diameter.   To do this, I drilled a counterbore about 0.600" deep with 0.625" bit.
 

Not shown:  Finished the bottom of the counterbore with a 0.625" endmill to achieve a clean, flat bottom.

With the holes finished, I faced the piece.

The counterbore for the barrel cover is easy to see here.

Moved to the milling machine and fly cut what will be the right and left sides of the breech.  The fly cutting was used to remove just a couple thousandths and produce a nice surface finish.

A multi-anvil micrometer was used to measure the wall thickness at each side of the counterbore.  One of the sides was thicker than the other by  0.003"--hardly enough to worry about, but I recut the high side until it matched. 

Next is the radius cut along the base of the breech to fit against the gas tube.

Caliper set at 0.3675" to scribe the center line.  I'll use it as a secondary reference and use an edge finder to find true center for the milling.



More soon.

Anschutz Front Sight Adapter for the Tech Force TF79 / AR2078A

Took a couple weeks off airgun posting due to increased workload at the shop.  It's a seasonal business and we're in full season.  I have been making things--but mostly machine tooling related items.  I managed to eek out a project yesterday for my TF79 target rifle.  I had already upgraded the rear target sight with a Baikal diopter, and recently found a spare Anschutz front sight in one of my parts bins.  Aside from the higher overall quality of the Anschutz unit compared to the TF sight, I've got a lot of inserts for the Anschutz, so it makes sense to get it onto the rifle.















A piece of 1" round aluminum predrilled with a 0.500" though hole will make for a good start.

The barrel OD on the Tech Force is 15mm--I don't have a 15mm bit and sorely need to buy one.  So, guess I'm doing it the hard way.

Through drilled with a 9/16" bit to provide clearance for a boring bar.

The boring bar barely fit, but that's enough.  Bored out the hole to just over 15mm.

Faced the end.

Used the compound to cut a taper.  Just eyeballed it, as there was no need for a specific angle.

With the taper done,  the piece was moved to the mill.  The card stock should help prevent marring the sides of the work from the vise jaws.  Just going to do something simple.  Again, no real measurements.  Only noted how deep the cut was.

Cut a flat.

Flipped the piece and cut a flat 180 degrees from the first.  Matched the depth of the first cut so they were equal.

A high speed pass on each side left a nice finish.





















Sanded the piece to 500 grit with an oil soaked piece of emery cloth. 

The Anschutz sight still patiently waits.

Needs dovetails as well as some set screw holes for mounting to the barrel.

The Tech Force barrel had a milled flat for a set screw exactly 120mm from the muzzle.  Lacking a proper height gage, (Yes, I'm a bit under-tooled) I adjusted a surface gage to the correct height and scribed the mark.

Did some rough layout for the dovetails.  The Anschutz sight looks like it requires 60 degree angles.

This was alarmingly uneventful.

Located the hole position for the first set screw.

It was spotted and drilled.

Then tapped M5 x 0.8mm--the largest size screw that would fit in the milled pocket on the TF barrel.

Decided to add two more set screws to the adapter.  

Just needs some clean up.

Sight screwed in place.

Installed.

I took some time to get the new front sight in a similar location height-wise from the bore compared to the old.  Had to do minimal rear sight adjustment to get on target.




Check back soon.